RUBY-1359 add HTTP status code to analytics events
RUBY-1359 Freeze string constants used as keys in RequestSampler
RUBY-1366: Allow customers to set display name for hosts.
edited configuration documentation to add information on how transaction_tracer.explain_enabled interacts with slow_sql.explain_enabled. This will help support and customers.
Add a -l option to list performance tests
Merge pull request #725 from ruby-agent/http-status-code-in-analytics-events

RUBY-1359 add HTTP status code to analytics events
Fix for 1.8.7 build breaks by guarding middleware results groveling better
Merge pull request #742 from ruby-agent/silly_middleware_results

Fix for 1.8.7 build breaks by guarding middleware results groveling better
Merge pull request #741 from ruby-agent/list-perf-tests

Add a -l option to list performance tests
Allow perf tests to take multiple measurements and sum them.
Also adds a test for ThreadProfile#generate_traces.
RUBY-1365: Small refactoring: changed the name of a method.
RUBY-1365: No need to create a bunch of arrays here.
RUBY-1365: Works, but needs cleanup.
RUBY-1365: Don't normalize data thread profile data when converting to collector array.
RUBY-1365: Split BacktraceNode into BacktraceNode and BacktraceRoot (inheriting from
BacktraceBase). Also got rid of `prune!` and `total_count`, as they were no
longer being used anywhere.
Changes from code review.
Merge pull request #740 from ruby-agent/RUBY-1365-no-more-recursion

RUBY-1365: No more recursion in BacktraceNodes
RUBY-1366: Better description.
Merge pull request #739 from ruby-agent/RUBY-1366-set-hostname-via-config

RUBY-1366: Allow customers to set display name for hosts.
RUBY-1359 Skip HTTP status codes if no middleware tracing

If we aren't doing full middleware tracing, we can't reliably get the
HTTP status code for appending to transaction events.